The invention concerns a rotary extrusion/blow-molding machine.
More particularly, it concerns machines provided with several molding units carried by a carrousel that is rotatable around an appreciably vertical axis. In a known way, each molding unit has a two-part mold, both parts being movable with respect to each other between an open position and a closed position.
These machines also have an extrusion head that is placed above the carrousel in a specific angular position around the carrousel""s axis of rotation.
Each mold is controlled to be in the open position when the corresponding unit is located below the extrusion head, and to close again after having seized a section of preform flowing from the extrusion head.
The invention is applicable more particularly in the case of machines in which each molding unit is mounted on the carrousel in a way that is movable between a working position and a retracted position to which it is taken just after the section of preform is seized.
The EP-A-0.284.242 document describes a machine of this type. In this instance it is a sequential type machine in which the rotation of the carrousel is not continuous.
The machine described in this document has molding units that can slide vertically with respect to the carrousel between an upper working position and a lower retracted position. Immediately after a molding unit has seized a section of preform, and until this unit has been released below the extrusion head by rotation of the carrousel, the molding unit is moved toward its retracted position. This makes it possible to prevent the preform from spilling over onto the upper face of the mold during extrusion in a situation in which the preform or preforms are continuously extruded.
The vertical sliding of the molding unit corresponds precisely to the direction of extrusion of the preform. The magnitude of the movement of the molding unit should therefore correspond to at least the length of preform that is extruded during the time the blow-molding unit is immobilized beneath the extrusion head. With this design, a free space must therefore necessary be provided beneath the working level of the molding units, to allow their retraction. This free space therefore significantly increases the total height of the machine.
Moreover, the slidable mounting of the molding units is particularly difficult to accomplish satisfactorily. Excellent guidance must be provided to ensure that the unit is perfectly stable, while still allowing relatively fast movement at the time the unit is released.
A purpose of the invention, therefore, is to propose an improved design of a machine of the type described above, this design allowing machines to be produced that have a high rate of production.
To that end, the invention proposes a machine of the type described above, characterized in that the molding unit is mounted on the carrousel in order to be able to tilt around an appreciably horizontal axis.
According to other characteristics of the invention:
the molding unit is articulated around an axis that is appreciably tangent to the path of the carrousel;
the axis of articulation is vertically off center with respect to the top of the molding unit in the working position so that, at the beginning of the tilting movement, the movement of the top of the molding unit has a horizontal component;
the part of the molding unit over which the extrusion head passes during the tilting movement has a chamfered shape;
the molding unit is mounted on a cradle that is articulated on the carrousel by an inner radial side with respect to the axis of rotation of the carrousel;
both parts of the molding unit are movable with respect to each other in a direction that is appreciably radial with respect to the axis of rotation of the carrousel;
the mold has at least two cavities that are offset along a direction tangential to the path of the carrousel, and the extrusion head (16) has as many dies as the mold has cavities in order simultaneously to furnish that many parallel preforms (15a, 15b) the separation of which corresponds appreciably to the offset of the cavities (30a, 30b);
the tilting of the molding unit from its working position to its tilted position is forced by drive means; and
the rotation of the carrousel around its axis is continuous.